"And this is the time of year when people and rattlesnakes are most likely to come into contact because they both like to be outdoors now." Some bite victims are simply in the wrong place outdoors at the wrong time.

A young rattlesnake bit 7-year-old Gianni Thomas on the foot June 3. He was on the back patio of his family's ranch home south of Pittsburg, Calif.

The snake, which was less than 16 inches long, sank its fangs into Gianni's right foot and didn't let go until the boy's older brother, William, yanked it away as venom squirted over the patio, said the boys' mother, Tina Thomas.

Gianni's leg swelled up and darkened, and he become pale and hallucinatory en route to a hospital, where he fully recovered after a four-day stay.

"It was terrifying," Tina Thomas said. "It's a risk on the ranch and, for that matter, for people who hike on trails in open land. You have to watch out and be careful."

Thomas said her family members see rattlesnakes every year, but they have seen more this year than in recent memory - at least 20 sightings so far.

On average, fewer than one of the rattlesnake bites in California are fatal each year.

Bee stings and dog attacks account for more deaths, but rattlesnake venom can kill humans and dogs; they also can lead to limb amputations.

As much as she admires their survival tactics and their signature rattle that warns unwelcome visitors, Colbert urges people to keep a distance from the only poisonous snake species in the San Francisco Bay area.

Few know rattlesnakes better than Colbert does. She works for the East Bay Regional Park District, and from 1998 to 2007, she did a research project in which she tracked 12 wild rattlesnakes at the Sunol-Ohlone Regional Wilderness that had radio transmitters sewed into their bodies.

Fred, Cleo, Lola and the rest of those snakes didn't wander too far from home, reaffirming her view that rattlesnakes are more like cautious homebodies than bite-happy bullies.

"Rattlesnakes are more like us than we think," said Colbert, who uses a captive rattlesnake named Fergie to make points in her nature education classes. "They like to go out in good weather. They get grumpy in hot weather. They want food, shelter, family and to avoid predators, but they will strike out if they feel threatened."

Researchers have found that many rattlesnake bite victims are young men who were drinking alcohol, said Patrick Roy, a spokesman for the state Department of Fish and Game.

Research also found that many victims are bitten in the hand or arm, indicating that the people either intentionally reached for a snake or reached into rocks, weeds or brush without taking precautions, Colbert said.

She recalls a visitor to Del Valle Regional Park near Livermore, Calif., who attempted to demonstrate to his child the best way to pick up a rattlesnake. The man ended up being rushed to the hospital for treatment of a bite.

The best advice, naturalists and public health experts say, is for people to leave rattlesnakes be unless it's in a place where it can't be avoided.

Back at the Sunol Regional Wilderness visitor center, Colbert recalls how her radio tracking over nine years honed her rattlesnake fascination.

She saw snakes swim across a creek and hang out together. She saw a snake curl up and wait for hours next to a barely recognizable path in the grass used by rodents.

While she knows more about rattlesnakes than most people do, Colbert said she knows not to feel confident because their behavior is unpredictable. "They can surprise you," she said.